1. Field of the Invention
The present invention relates to a high-speed video camera using a solid-state image pickup element.
2. Description of the Prior Art
In regard to means of high-speed image pickup for home video recorders and color video cameras employed widely for industrial purposes and using MOS-type or CCD-type solid-state image pickup elements, there is a system wherein high-speed scanning and sequential reading are conducted with increased horizontal and vertical drive frequencies. There is also another system, in this regard, wherein an image is divided into a plurality of areas or blocks, and parallel and simultaneous scanning of photoelectric conversion element rows in each block is conducted sequentially for each block, so as to attain a high speed reading.
In the known reading systems described above, the former system is similar to a standard television system, wherein reading is conducted by driving the solid-state image pickup elements at a high speed. Given that a practical number of pixels is supposed to be two hundred fifty thousand or above, the number of stages of MOS shift registers constituting the scanning circuit becomes large and a clock frequency increases in proportion to the speed of scanning. As a result, increases in the wiring capacitance of the clock circuit and the rise time of the clock pulse itself produce adverse effects and consequently, the shift registers are unable to follow the scanning. Moreover, MOS-type elements are problematic due to the capacitances of horizontal and vertical signal lines, while the CCD-type ones have limitations with respect to high-speed scanning caused by the impairment of transfer efficiency.
The above-mentioned latter system is one wherein an image is divided into a plurality of areas or blocks, all the photoelectric conversion element rows in one block are read in parallel and simultaneously, and then the blocks are read sequentially, as disclosed in the National Publication of Translated Version No. 501704/1981. However, this system necessitates a specific solid-state image pickup element which scans all of the photoelectric conversion element rows in one block in parallel and simultaneously, and includes a number of mechanisms for taking out all signals produced by scanning in parallel and simultaneously, and circuits for amplification and processing thereof. Furthermore, an electronic means for recording the signals after reading them out is complicated and accompanied by difficulties in manufacture.
Accordingly, the scanning speed obtained by the above-mentioned former system of the prior art described above is at best two to three times higher than that of standard television (the scanning speed of standard television is 50 to 60 fields per second), and it is impossible to realize scanning at a higher speed than the above using the solid-state image pickup element employed in standard television. On the other hand, the above-mentioned latter system has a shortcoming in that it necessitates that the specific solid-state image pickup element has mechanisms for delivering a plurality of pixel selecting pulses simultaneously from the same vertical shift register and for processing the obtained outputs simultaneously.